Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session C06: Flames |
Hide Abstracts |
Chair: Antonio L. Sánchez, UCSD Room: 205 |
Sunday, November 24, 2019 8:00AM - 8:13AM |
C06.00001: Blue whirl structure revealed Joseph Chung, Xiao Zhang, Carolyn Kaplan, Elaine Oran The blue whirl is a newly discovered whirling flame which shows only blue emission and burns liquid hydrocarbon fuels. It begins as a large, sooty fire whirl which decays to the self-sustaining, soot-free blue flame. Details of its structure were unknown in part due to difficulties in experimental diagnostics. This work presents numerical simulations of the blue whirl, which reveal its flow structure and burning modes for the first time. The numerical model solves the unsteady, compressible, Navier-Stokes equations. The effects of combustion are modeled using a calibrated chemical-diffusive model. The domain is a cubical enclosure with sides which are 30 cm long. Circulation is imposed by forcing air through the corners and a constant flux of fuel is specified at the center of the bottom floor within a specified diameter. The upper boundary is an outflow condition and all other boundaries are non-slip. The results reveal a triple flame structure within the blue whirl and the influence of vortex breakdown on its burning and flow structure. [Preview Abstract] |
Sunday, November 24, 2019 8:13AM - 8:26AM |
C06.00002: Numerical description of blue whirls over liquid-fuel pools Antonio L Sanchez, Jaime Carpio, Wilfried Coenen, Elaine Oran, Forman A Williams Previous experiments of liquid-pool fires with ambient swirl have shown that, when the outer circulation is increased beyond a critical value, the existing fire whirl transitions to a new, fundamentally different configuration involving a lifted partially premixed front lying below a recirculating-flow bubble. The steady axisymmetric structure of this so-called blue whirl is investigated here by numerical methods. The problem is formulated with account taken of the boundary velocity induced by the thermal plume developing vertically above the axis, with a one-step Arrhenius description adopted for the heat release and a simple, optically thin approximation for H$_2$O and CO$_2$ radiation, the latter being fundamental for fuel vaporization. Integrations for increasing values of the swirl level are seen to describe all of the flow features observed in experiments, including the detachment and subsequent lifting of the flame edge, the emergence of vortex breakdown, and the establishment of a partially premixed front with a stoichiometric ring. [Preview Abstract] |
Sunday, November 24, 2019 8:26AM - 8:39AM |
C06.00003: Understanding Combustion in the Blue Whirl using Optical Diagnostics Sriram Bharath Hariharan, Yejun Wang, Paul M. Anderson, Waruna D. Kulatilaka, Michael J. Gollner, Elaine S. Oran The blue whirl is a soot-free flame that evolves from a traditional fire whirl in a regime close to the extinction limit for fire whirls. Previous work considered the physical and thermal structure of the flame and scaling approaches to predict transition to the blue whirl. To better understand the exact nature of combustion in the blue whirl, the present work uses chemiluminescence and planar laser-induced fluorescence (PLIF) techniques to visualize the reaction zone and distribution of radicals in the flame. Chemiluminescence images of excited-state OH* and CH* were obtained at 1 kHz and converted into a radial map using Abel inversion and the OH*/CH* intensity ratio was computed for the region around the bright blue vortex rim. A relationship between this ratio and the local equivalence ratio ($\Phi \in $[0.7,1.3]) was obtained by extrapolating from adiabatic methane-air flames stabilized over a Hencken calibration burner. In addition, PLIF images show that ground-state OH exists in high concentrations in the region of the bright blue ring and diminishes gradually into the post-flame region. Negligible presence of OH was observed in the blue conical region below the ring. [Preview Abstract] |
Sunday, November 24, 2019 8:39AM - 8:52AM |
C06.00004: On the Consistent Flamelet Model Formulation for Transcritical Fluid Flow and Combustion Zheng Qiao, Yu Lv Fluid flows in transcritical thermodynamics conditions have numerous applications in combustion engines and thermal energy devices. Under such conditions, the fluid behaviors are largely affected by the peculiar viscous transport properties and nonlinear thermodynamic relations. To achieve cost-effective modeling of transcritical fluids, the flametlet model has been exploited and investigated by a number of studies. This study focuses on the effects of model formulations on the flamelet predictions of transcritical fluids in both pure-mixing and combustion conditions. We first derive the consistent flamelet formulation based on Pitsch {\&} Peters (1998) and then examine the constant Lewis assumption and the interspecies enthalpy flux on the flamelet predictions. For illustration purpose, the H2/air system at various thermal conditions is considered. Our study concluded that it is of importance to consider the detailed consistent model formulation in flamelet modeling of transcritical fluids. [Preview Abstract] |
Sunday, November 24, 2019 8:52AM - 9:05AM |
C06.00005: Modeling and Simulation of a H2/O2 Diffusion Flame under Cryogenic Condition using a Consistent Flamelet Formulation Yu Lv, Zheng Qiao Modeling of combustion phenomena under supercritical/transcritical conditions has recently gained growing attentions with the increasing applications of high-pressure combustion and energy devices.~ Under such thermodynamic conditions combustion dynamics and flame characteristics are strongly impacted by the peculiar thermo-diffusive transport properties and the nonlinear equation-of-state relation. In this study, we first illustrate the those affects through a flamelet study in which the comprehensive and consistent flamelet model is compared against the commonly used flamelet model formulation. Then the consistent flamelet model is employed to the LES of a GH2/LOx cryogenic flame based upon a newly developed computational framework. The simulation results will be extensively discussed and compared qualitatively with the experimental measurements by Candel et al. (2006).~ [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700